Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 89 (2004) 614-628
Model pyroxenes II: Structural variation as a function of tetrahedral rotation
model with O3-O3-O3 angle = 120 and model oxygen radius = 1
Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
_database_code_amcsd 0003477
6.6332 6 3.464 90 100.0 90 C2/c
atom     x      y      z
Mg1      0  11/12    1/4
Mg2      0    .25    1/4
Si    5/16   1/12   3/16
O1     1/8   1/12    1/8
O2     3/8    .25    3/8
O3     3/8   1/12    7/8